Psychologists distinguish between two kinds of errors that

people make when reasoning:

✓ Motivational or ‘hot’ illusions: These stem from the

influence of emotions and assessments of personal

interests upon the reasoning. For example, most people

assume that their views now will stay the same for

the foreseeable future, and fiercely defend them, even

though, in reality, most people’s views change and evolve

all the time.

✓ Cognitive or ‘cold’ illusions: Stem from errors in

your reasoning: things like mixing up correlation and

causation (two things may keep happening together

but that doesn’t actually mean one caused the other)

or having an unconscious bias in favour of information

which fits with your existing views.

Many researchers consider that because both kinds of errors

are so common, indeed almost universal, they must have

some kind of evolutionary purpose, indeed advantage, for the

human species.

What most people would call sloppy reasoning allows for

quick responses and so may increase the chance of survival in

situations where a lack of time or of background information

can be fatal.

Plenty of research also suggests that people who distort

assessments in favour of their own self‐interest, perhaps

inflating their achievements and capabilities in job interviews

or in reports, do better in life. Perhaps, paradoxically, self‐

deception can enhance people’s motivation, mood and even

productivity.